Polar Bears on Thin Ice in New IMAX Movie

Polar bears are in a desperate struggle for survival and the U.S. Geological Survey warns that the population of 25,000 could shrink two-thirds by 2050 as the Arctic Sea keeps warming and the ice continues to melt. The warming causes bears to be separated from their hunting grounds, forcing them to swim for days in order to reach suitable ice flows.

In the new IMAX movie " To the Arctic," narrated by Meryl Streep which opens on Friday, the filmmakers followed one mother bear as she swam for nine days in order to reach an ice flow big enough to support the hunt for seals. Her cub did not survive the swim.

The bears are superb swimmers, but their nearly foot wide paws are not intended to keep the marine carnivore afloat for more than a couple of days at a time.

"A lot of bears are swimming further to get food. The cubs are having a tougher time," filmmaker Greg MacGillivray told ABC News.

As the polar bear population continues to decline, zoos are being looked at as a way to safeguard the species. There are campaigns to build polar bear DNA banks and breeding laboratories at zoos across the country. The St. Louis Zoo is in the process of building a $20 million exhibit for up to five bears. It is scheduled to open in 2017.

"In the 1940s we had about 200 polar bears in North America. Now we are down to 64. We need to bring more bears in so that we can maintain a genetically viable population off into the future," said Dr. Jeffrey Bonner, president of the St. Louis Zoo. "We will always have populations of bears in the wild as far as we can see into the future, but those populations may be fragmented. We may have to augment their genetics by moving genetic material from bears like here in the St. Louis Zoo out into the wild."

For polar bears greater diversity means an increased chance of survival over the long-term.

"The more diversity we can have in the population, the better because it makes the bears overall much more able to stand up to things like climate change, it makes them be able to adapt better," Meredith Wagoner, Mammal Collection and Conservation Manager at the Maryland Zoo, told ABC News.

While zoos may be able to help prevent extinction in the future, Bonner says it's not too late to reverse course so the Arctic does not reach that point.

"Remember, animals are safe in zoos, they are not saved in zoos," Bonner said. "We need to motivate our entire country to change their behavior in such a way that the Arctic is a safer place and we can do that. We are not out of time."